1. Technical Field
This invention relates generally to internal combustion engines. More specifically, it relates to fuel injectors for such engines. I have invented an electromagnetic fuel injector drive motor and pump of minimum size and minimum electric power requirements. The motor and pump meters a volume of liquid fuel at high pressure for spraying into the headspace of compression ignition or spark ignition internal combustion engines.
2. Background Art
For two-stroke spark ignition (SI) engines, for example, injection of fuel directly into the headspace above the piston in a cylinder has important advantages. If injection is timed late enough, no fuel is blown out the exhaust during scavenge. This raises the thermal efficiency and reduces the unwanted emissions that have for so long blemished the performance of carbureted two-stroke engines.
Head-injected two-stroke compression-ignition (CI, or Diesel) engines have existed since before 1930. But an SI engine borrowing the injector technology of any existing Diesel will not usually have as high a power output per unit weight as the same SI engine using a carburetor. Carbureted SI engines tend to have higher outputs per unit weight than CI engines because they can run at higher speeds. This is because fuel injection into an engine headspace must achieve a useful fuel/air mixture within limits of time and turbulence that become more constraining as the engine speed increases. On the other hand, there is no limit to the speed of a carbureted engine because whatever time and turbulence is needed to create a uniform fuel/air mixture can be provided by a carburetor and intake system.
An object of this invention is to provide a head-injection system for SI two-stroke engines which will enable higher engine speeds so that the power output per unit weight can approach that which would have been possible had a carburetor been used.
A head injector must act to atomize, vaporize, and mix fuel with as much as possible of the air within the head-space. Existing head-injection systems for SI two-stroke engines have disadvantages.
Some of them have mechanically operated fuel pumps. The blow-by of such pumps results in reduced and uncontrolled fuel delivery at low speeds such as idle, and the rate of mass-flow through the nozzles varies with engine speed. Therefore most recent work in the field of fuel injection for SI engines uses electrical injector pumps or electrical flow valves. This invention concerns a novel electromagnetic fuel pump that has special capabilities. The linear motor and pump of this invention provides a mass flow through the spray nozzle which is substantially independent of engine speed and delivery volume. The spray characteristics of the spray valve can therefore be more precisely tailored than others.
Some existing head-injection systems use compressed air at typically 5 atmospheres to help atomize fuel valved into the injector at 2 atmospheres. The fine spray so produced could have been achieved without the need for compressed air by pumping fuel into an appropriate nozzle at 50 or more atmospheres pressure. The linear motor fuel pump of this invention is capable of injection pressures up to 200 atmospheres so enabling usefully fine sprays without the expense of providing an air compressor.
Objects of this invention which generally advance the state of the art beyond its present boundaries include:
An electromagnetic fuel motor and pump of minimum size for a given efficiency of converting electrical power input to flow power output. Because of the limited engine compartment volume needed for spark plugs and cooling, this is important.
An electromagnetic fuel motor and pump where the volume of high pressure fuel existing in the voids of plumbing, flow valves, spray formers etc., is a minimum. This reduces the hazards of high pressure fuel, avoids pressure and flow pulsations which often plague the development of high-pressure injectors, and avoids significant energy storage due to fuel compressibility which could complicate matching the linear motor output force to the force required by the pump.
U.S. Pat. No. 3,353,040 (Abbott) discloses an electromagnetic motor for converting electric power to reciprocating mechanical power. The motor in this patent is used to ensonify the ocean with audible or super-audible sound waves.
U.S. Pat. No. 4,004,258 (Arnold) discloses a position-indicating solenoid with a ferromagnetic plunger movable between two stops, and fixed permanent magnets which cause the plunger to adhere to the stop to which it is moved. Movement of the plunger is accomplished by a winding about each stop which when excited by an electrical pulse exerts an attractive force on the plunger.
U.S. Pat. Nos. 4,046,112 and 4,572,433 (Deckard) disclose an electromagnetic fuel injector with a solenoid actuated valve for controlling the flow of fuel through bleed orifice and charge orifice passages.
U.S. Pat. Nos. 4,090,097, 4,123,691 and 4,278,904 (Seilly) disclose an electromagnetic motor with an annular member and a core member interengageable by screw threads.
The technical paper, Low Pressure Electronic Fuel Injection System for Two-Stroke Engines by Edmond Vieilledent, published by the Society of Automotive Engineers, Inc., Technical Paper Series 780767 (1978), describes different fuel injection systems which the Motobecane Company tested for several years, and discloses a direct electronic injection system, using electromagnetic injectors, specially adapted to the two-stroke engine.
U.S. Pat. Nos. 4,129,253, 4,129,254, 4,129,255 and 4,129,256 (Bader et al.) disclose electromagnetic fuel injectors of the same general construction as U.S. Pat. Nos. 4,046,112 and 4,572,433 (Deckard), discussed above.
U.S. Pat. Nos. 4,545,209 and 4,578,956 (Young) disclose a linear driver motor for a cryogenic split Sterling refrigerator. The motor includes a permanent magnet mounted to the moving armature of the motor which in turn drives a piston element.
U.S. Pat. No. 4,804,314 (Cusack) discloses a fluid injection pump with an outer cylinder made of a negative magnetostrictive material, and an inner piston made of a positive magnetostrictive material. When a magnetic field is applied to the assembly, the cylinder contracts and the piston expands to expel fluid past a head valve through an injection port.
U.S. Pat. No. 4,844,339 (Sayer et al.) discloses a fuel injector with an electromagnetic fuel metering valve.
U.S. Pat. No. 5,011,082 (Ausiello et al.) also discloses a fuel injector with an electromagnetic fuel metering valve.